Electronic devices, such as various sensors, accelerometers and the like, are routinely enclosed within a housing to provide protection to the electronic device from the environment. Most often, such housings are formed from a polymeric material which offers low weight as well as desirable mechanical and dielectric properties. To provide electrical leads from the exterior of the housing to the accelerometer within the housing, an electrically conductive lead frame is conventionally used. A lead frame is generally a stamped metal part consisting of a number of leads, or terminals, integrally formed with a sacrificial frame that supports the leads during the forming, assembly and molding operations. Once the leads are properly molded in place with the housing, the frame is removed to prevent direct electrical contact between the leads.
To interconnect the leads with their corresponding conductors on a circuit board to which the housing is to be mounted, the leads must typically be appropriately bent toward the circuit board substrate. Generally, this forming operation occurs either before or after the molding operation. If performed before the molding operation, the lead frames are stamped and formed off-line, and then placed directly in the mold prior to injection of the plastic into the mold, with no further forming operations being required to form the leads other than the removal of the sacrificial frame.
While such an approach is generally accepted by the industry, an inherent shortcoming is the difficulty associated with the handling of the lead frames due to the irregular shape of the formed leads. Particularly, if an automated magazine feed system is to be used to facilitate the assembly and molding operation, such as with robots or other automated equipment, the shape of the formed and bent leads makes it difficult to stack the lead frames within the magazine. Inherently, the design of the magazine must be specially adapted to accommodate and feed the lead frames to the molding station. However, the irregular shape of the bent leads will still pose the potential for an increased number of misfeeds.
To avoid the above problems associated with a preformed lead frame, the leads may be formed after the molding process. While this approach generally overcomes the handling problems associated with the former method, the requirement for a secondary operation to form the leads is typically undesirable from an economic and processing standpoint, in that each additional operation requires added time, labor and equipment.
Thus, it would be desirable if a lead frame could be delivered by a magazine system to a molding station at which the lead frame is to be molded with a plastic electronic housing, without requiring the lead frame to be preformed prior to being fed to the molding station. Furthermore, it would be desirable if the electronic housing did not require a secondary operation to appropriately form its leads after the lead frame has been molded into the housing.
Accordingly, what is needed is a method and apparatus by which the required forming operation and molding operation can be merged, such that the forming operation occurs while the lead frame is secured within the mold cavity during the molding operation, so as to enable as-stamped lead frames to be fed directly to the molding station, and thereby also alleviate the requirement for a post-molding secondary operation to form the leads.